Bicycles have been used for transportation for many years. Recently, bicycles have been increasingly utilized for exercise and health reasons. Further, there are many different types of bicycles for different purposes such as racing, traversing unpaved train and touring.
Many bicycles include multi-speed transmissions to enhance their operational over different types of train. Existing bicycle transmissions are generally derailleur type manually controlled by a cable connected to a shift lever. Moving the shift gear changes the cable tension and moves the derailleur and a drive chain from one gear to another gear. With different gearing ratios, different pedaling effort and speeds can be accomplished.
A disadvantage of existing transmissions is lack of a mechanism for automatically shifting the transmission to reduce the pedaling effort when the bicycle is slowed due to breaking by a rider. This is particularly problematic in cases where before stopping the bicycle transmission has been shifted for high speed travel. Then when the rider stops, the rider must exert a large amount of pedaling force to start the bicycle moving again. An automatic downshifting a mechanism would relieve the rider of having to remember to shift the transmission for reducing the pedal effort when the rider slows the bicycle under breaking action.
There is therefore a need for a multi-speed transmission for a bicycle which provides automatic downshifting when the user applies the bicycle breaks.